Salt Water Pools - Salt/Chlorine Generators


IMPORTANT WARNING:
  If you do not properly maintain a salt/chlorine generator, or your pool chemistry when using a salt/chlorine generator, you can destroy your pool’s interior finish, decking and pool equipment!  Salt water pools need a great deal of care.  (14).

Salt/chlorine generators are a method which employs both technology and traditional chemical use to sanitize swimming pools.  In the interest of providing comprehensive information regarding swimming pool treatment methods, salt/chlorine generators are included; however, salt/chlorine generators are not recommended for residential swimming pools due to reported problems related to high operating costs, corrosion, salt damage to pool structures and equipment, lack of reliability/high failure rates, environmental and health issues.  (16, 17).

Swimming pools utilizing salt/chlorine generators are sometimes referred to as saltwater pools.  Some people feel that the effect of the salt water on their skin is preferable to traditional chlorination methods; opinions vary on that aspect of saltwater vs. traditional chlorination.

Salt/chlorine generators typically are installed and sold as a “bell and whistle” when a new pool is built, with little or no regard for the owner’s operating cost or ability to properly operate and maintain the system over time.  They work by putting salt (sodium chloride) into the swimming pool so that the salt concentration is between 2,500-6,000 ppm. (13)  The pool water is filtered and it passes through the salt/chlorine generator where the process of electrolysis occurs.  Some salt/chlorine generators use a salt or brine tank as the salt supply for the salt/chlorine generator.  This type of system is used less often than the generators that use the swimming pool water itself as the salt supply.  (14) Our focus will be on the more common salt/chlorine generators which use the swimming pool water itself as the salt supply.

Electrolysis is a process where electrical current is applied to two parallel electric plates which convert salt water into hypochlorus acid and sodium hypochlorite or liquid chlorine bleach.  Salt water pools are not “chlorine free” as the salt/chlorine generator actually produces the liquid chlorine on-site from the salt contained in the swimming pool water. (13)

Salt/chlorine generators reduce the amount of handling and storage of liquid chlorine bleach or chlorine tablets, but do not reduce the need for other chemicals such as acid, alkalinity increaser and occasional “shocking” with liquid chlorine bleach to eliminate algae and restore water clarity.  Also, the internal cells of the salt generator require periodic acid washing.

Salt/chlorine generators require additional electrical and plumbing connection, lines and piping, over and above those required for traditional plumbing of the pool pump and filtration equipment.  They also require significant amounts of electricity for their operation – a cost element which must be considered when comparing salt/chlorine generator costs with traditional chlorination methods.

The electrolysis process has been used in many applications to achieve chemical reactions.  The two parallel plates in the salt/chlorine generator have different electric charges.  As a result they attract opposite charged material dissolved in the pool water.

As the electrolysis process occurs as the swimming pool water passes through the electric plates, dissolved calcium or other dissolved minerals can begin to accumulate on the plates which, over time, reduces their effectiveness to produce chlorine and increases electricity usage.  Left unchecked, the salt/chlorine generator can become ineffective at sanitizing the pool, resulting in algae and poor water quality.  Accordingly, meticulous maintenance of the electric plates is essential in maximizing the salt/chlorine generator life and its ability to produce chlorine. 

Periodically, additional salt must be added to the pool to counter salt dilution caused by rainfall and the addition of pool make-up water to compensate for evaporation, filter backwash and splash-out.  In addition to testing the pool water for pH and chlorine levels, the pool salt concentration also must be monitored frequently.

Salt/chlorine generators produce chlorine continuously while the pool pump is operating.  Thus, the selection of a correctly sized salt/chlorine generator is critical.  If the unit is too small, it will produce an insufficient amount of chlorine and will not meet the pool’s chlorine demand.  If the generator is too large it will produce too much chlorine, which will increase the pH of the water and, in turn, will reduce the effectiveness of the chlorine and cause a significant increase in the amount of acid required for pH control.

The pH and chlorine relationships are just as important in pools using salt generators as they are in pools using liquid chlorine bleach or chlorine tablets.

Some manufacturers of salt/chlorine generators include in the equipment monitoring devices to assist in controlling the salt to chlorine output of their equipment.  These systems are significantly more expensive than salt/chlorine generators that rely on the pool owner or operator to monitor the chlorine levels and pH of the pool.

Salt / Chlorine Generators:    Special Construction Requirements       Other Pool Chemicals Needed       Maintenance Requirements       Long Term Costs

 
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